This invention relates generally to the field of aerosolization, and in particular to the aerosolization of liquids, such as drug formulations for inhalation by a user. In one specific aspect, the invention relates to the production of an aerosol using an aerosol generator, with the aerosol generator being configured to stop aerosol production at a time selected to permit the remainder of an inhaled breath to clear any inhaled aerosol from the effective anatomical dead space and move the inhaled aerosol into a targeted portion of the respiratory tract such as the lungs.
Aerosol inhalation is useful in a variety of drug delivery applications. Aerosol delivery provides numerous advantages over other drug delivery channels such as injection, ingestion and intravenous delivery. A variety of apparatus exist for aerosolizing medicaments. Merely by way of example, U.S. Pat. Nos. 5,140,740, 5,938,117, 5,586,550, 5,758,637, and 6,014,970, the complete disclosures of which are herein incorporated by reference, describe various apparatus useful in aerosolizing liquid medicaments that a user may inhale through a mouthpiece. Apparatus for aerosolizing liquid medicaments may also be incorporated into the airflow circuit of a ventilator where a ventilator is used to provide inspiratory airflow to a patient.
One factor that may be of interest with respect to inhaled aerosol drug delivery is the amount of drug reaching predetermined target areas of the respiratory tract, where the drug can be most effective, compared to the total amount of drug that is aerosolized. It is possible that a portion of aerosolized drug that is inhaled toward the end of an inspiratory breath may not reach the target tissue and may remain in untargeted portions of the respiratory tract, such as the upper respiratory tract, where it will not be effective. Thus, such region where an inhaled drug will not be effective can be said to comprise the effective anatomical dead space of the respiratory tract, because the inhaled drug will not reach the targeted portions of the respiratory tract and will be exhaled without having been utilized by the body of the user.
Thus, it is possible that a user may receive a smaller amount of drug than a chosen aerosol dose. This could result in a user being under-medicated or in the calculation of an inappropriate dose amount. In addition, such lost amounts of drug can adversely impact on the financial cost of a particular therapy. Further, such unused drug, when it is exhaled into the ambient air in what may be referred to as a puff, can be inhaled by other people in the vicinity of the user. Such individuals may be affected by inhaling what could be referred to as second-hand medication.
Accordingly, there is a need for systems and methods to reduce the amount of aerosolized drug that is unused, because it remains in the effective anatomical dead space, by clearing such aerosol from dead space in the respiratory tract so that a greater portion of the aerosolized drug reaches a chosen target region.